The goals of this research proposal are to elucidate the molecular signaling pathways that contribute to tumor development and physiology in the hamartoma syndromes resulting from loss of the tumor suppressor genes TSC1, TSC2, LKB1, and PTEN, and to identify and explore potential therapeutic targets. This research will provide insight into the pathogenesis of tuberous sclerosis complex (TSC), Peutz-Jeghers syndrome (PJS), and the variety of PTEN syndromes (e.g., Cowden disease), and will also have broader implications since the pathways these tumor suppressors control are activated in the majority of the common adult malignancies. A multi-tiered approach will be used for these studies, involving biochemistry, cell biology, yeast genetics, Drosophila genetics, high-throughput screens, genomics, proteomics, a variety of mouse models, and human tissue samples. These approaches will be used in a highly complementary and collaborative manner toward a more complete understanding of the cellular functions of these tumor suppressors and the pathways they regulate. Project 1 (Kwiatkowski/Manning) -- Tuberous Sclerosis-Pathway and Pathogenesis: evaluate the in vivo role of phosphorylation sites in TSC2 function, explore feedback regulation in TSC cells and tumors, explore how estrogen influences growth in TSC, and identify Rheb signaling events and interacting proteins;Project 2 (Cantley) -- LKB1/AMPK Signaling and Peutz-Jeghers Syndrome: examine the function of LKB1/AMPK in regulation of TSC2 and its cross talk with PI3K-AKT signaling and test a novel benign therapeutic approach for tumors arising in mouse models of PJS and TSC;Project 3 (Perrimon) -- Dissection of Tsc1/Tsc2/TOR/S6K Signaling in Drosophila: perform hypothesis driven RNAi screens to identify additional pathway components and perform genome-wide RNAi screens for regulators of AMPK, Akt and effectors of Tsc1/Tsc2-Rheb signaling. These projects will be supported by cores for Administration (Kwiatkowski), Mass Spectrometry and Proteomics (Cantley), and Human Pathology and Immunohistochemistry (Wu). Collectively these studies will enhance an ongoing effort among these investigators to understand the pathways that cause these hamartoma syndromes, and are critical in cancer development in general, for the purpose of identifying potential points of therapeutic intervention.